In some cases it may be necessary not only to adjust the angle or the alignment of a vehicle exterior mirror, but also to adjust its distance from the vehicle body. Such a length adjustment can, for example, be necessary in a vehicle with an extra-wide trailer to offer the driver an adequate view to the rear. If no extra-wide trailer is to be pulled, the vehicle exterior mirror which is protruding far outwards can be brought nearer to the body via the length adjustment, which not only has aerodynamic advantages, but also the risk of damaging the exterior mirror when parking or driving through narrow passages decreases.
From the publication DE 39 38 961 A1, a telescoping adjustment for an exterior mirror is known. In this case, the exterior mirror is attached to a continuously adjustable telescopic tube, which in turn is articulated by means of two flat profiles of a holding frame on the vehicle cabin. This open design of the mirror means is not only problematic from an aerodynamic point of view, but also has the disadvantage that the joint and also the telescopic tube are exposed to the elements. Since round telescopic tubes are not only displaceable, but also rotatable with respect to each other, the length adjustment in such an arrangement must also be able to receive torques which are applied by external forces onto the mirror.
Therefore progress has been made here using rectangular tubes which are mutually displaceable but not rotatable. The fixing of a defined relative position of the square tubes relative to each other has been achieved for example via a two-sided clamping. The previously mentioned problems of the aerodynamic behaviour and protection from the elements were addressed by assembling a housing around the telescopic means, said housing being formed from two pressure cast halves which are screwed together.
In practice however, it has been shown that this solution is not only heavy, but also does not satisfy in all cases the strength requirements for the force application from the exterior mirror to the holder mounted on the vehicle or the vehicle frame.